Milliner et al. International Journal of Emergency (2019) 12:7 International Journal of https://doi.org/10.1186/s12245-019-0224-0

PRACTICE INNOVATIONS IN EMERGENCY MEDICINE Open Access A pilot study of improvised CPAP (iCPAP) via face mask for the treatment of adult respiratory distress in low-resource settings Brendan H. Milliner1* , Suzanne Bentley2,3 and James DuCanto4

Abstract Background: Continuous positive airway pressure (CPAP) is a mode of non-invasive ventilation used to treat a variety of respiratory conditions in the emergency department and intensive care unit. In low-resource settings where ventilators are not available, the ability to improvise a CPAP system from locally available equipment would provide a previously unavailable means of respiratory support for patients in respiratory distress. This manuscript details the design of such a system and its performance in healthy volunteers. Methods: An improvised CPAP system was assembled from standard emergency department equipment and tested in 10 healthy volunteers (6 male, 4 female; ages 29–33). The system utilizes a water seal and high-flow air to create airway pressure; it was set to provide a pressure of 5 cmH2O for the purposes of this pilot study. Subjects used the system in a monitored setting for 30 min. Airway pressure, heart rate, oxygen saturation, and end-tidal CO2 were monitored. Comfort with the device was assessed via questionnaire. Results: The system maintained positive airway pressure for the full trial period in all subjects, with a mean expiratory pressure (EP) of 5.1 cmH2O (SD 0.7) and mean inspiratory pressure (IP) of 3.2 cmH2O (SD 0.8). There was a small decrease in average EP (5.28 vs 4.88 cmH2O, p = 0.03) and a trend toward decreasing IP (3.26 vs 3. 07 cmH2O, p = 0.22) during the trial. No significant change in heart rate, O2 saturation, respiratory rate, or end- tidal CO2 was observed. The system was well tolerated, ranked an average of 4.0 on a 1–5 scale for comfort (with 5 = very comfortable). Conclusions: This improvised CPAP system maintained positive airway pressure for 30 min in healthy volunteers. Use did not cause tachycardia, hypoxia, or hypoventilation and was well tolerated. This system may be a useful adjunctive treatment for respiratory distress in low-resource settings. Further research should test this system in settings where other positive pressure modalities are not available. Keywords: Continuous positive airway pressure, Emergency airway management, Critical care, Low-resource settings

Background airway pressure and regulate the respiratory cycle. How- Continuous positive airway pressure (CPAP) is commonly ever, in many low- and middle-income countries (LMIC) used as a means of respiratory support in patients with re- and global health settings, ventilators and CPAP devices spiratory distress in both hospital and pre-hospital settings may not be readily available. Respiratory distress and re- [1–3]. CPAP has been shown to reduce symptom burden, spiratory failure have been identified as key areas in which decrease intubation rates, and may reduce mortality rates the implementation of technology in low-resource settings [4–6]. In US hospitals, CPAP involves the use of a mech- has not been sufficient to meet the needs of patients [7, 8], anical ventilator or purpose-built CPAP device to generate and an alternative means of providing CPAP would help to address this unmet need.

* Correspondence: [email protected] 1Division of Emergency Medicine, University of Utah, 30 N 1900 E 1C026, Salt Lake City, UT 84132, USA Full list of author information is available at the end of the article

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Milliner et al. International Journal of Emergency Medicine (2019) 12:7 Page 2 of 6

The pediatric literature describes “Bubble CPAP,” a low-tech means of generating airway pressure by bubbling expired air or oxygen through a fixed amount of water. Bubble CPAP is delivered via nasal prongs and has been successfully used in neonatal respiratory distress both in US hospitals and in low-resource settings [9–12]. This approach has not been studied for use in adult respiratory distress. The respiratory setup described in this manuscript (termed “improvised CPAP” or iCPAP) is based on the principle of bubble CPAP and intended as a means of providing adult CPAP when a ventilator is not available. The system, detailed below, combines a respiratory mask and tubing with a high-flow source of medical air or oxygen and a water seal to generate airway pressure. Due to its simplicity, the system can be assembled out of basic respiratory equipment. This manuscript describes a pilot study of the iCPAP system in healthy volunteers to deter- mine its ability to reliably generate positive pressure and to provide initial safety data.

Methods Subjects Ten healthy emergency medicine residents were in- cluded. Six participants (60%) were male; the average age was 30 years (range 29–33). Volunteers with ac- tive pulmonary disease, a history of pneumothorax, severe claustrophobia, and pregnant subjects were excluded.

Device design and operation Fig. 1 Overview of the device. The iCPAP device has been fitted to A respiratory face mask was attached to a Y-shaped a simulation mannequin with basic components labeled airway connector; one end of the connector was capped while the other was connected to a 6-ft length of airway tubing submerged in a container of Device trials sterile water. High-flow medical air at 30 l/min was Device trials were carried out in a monitored simu- piped into the system near the capped connector lation center environment. Subjects wore the iCPAP using a separate port. For the purposes of this trial, setup during normal breathing for 30 min. Airway a respiratory pop-off valve, an end-tidal CO2 pressure data were continuously recorded at 0.1 s in- monitor, and a laptop-based airway pressure meas- tervals. Subjects’ heart rate (HR) and oxygen satur- urement device (Phidgets, Inc.) were interposed be- ation (SpO2) were continuously monitored and tween the face mask and the water reservoir (see recorded every minute, while end-tidal CO2 (EtCO2) Figs. 1 and 2). was recorded at 5-min intervals. At the conclusion During inhalation, positive pressure in the iCPAP sys- of the trial, each subject completed a brief question- tem is created by the rapid inflow of air from the wall out- naire evaluating his or her experience with the de- let. During exhalation, the force required to exhale vice (Additional file 1). through water in the reservoir creates positive expiratory pressure (Fig. 3). For the purposes of the current study, Data analysis the exhalation tubing was fixed 5 cm below the surface of The visual programming software Max (Cycling ‘74) the reservoir, generating 5 cmH2O of expiratory pressure; was used for pressure data sampling. Raw pressure depth can be adjusted to vary the supplied pressure. data was separated into inhalation and exhalation Milliner et al. International Journal of Emergency Medicine (2019) 12:7 Page 3 of 6

Fig. 2 Enhanced view of the mask and attached components

Fig. 3 Flow patterns. During inhalation, air flows from the wall outlet to the mask. During exhalation, air travels from the patient through the exhalation limb to the reservoir Milliner et al. International Journal of Emergency Medicine (2019) 12:7 Page 4 of 6

phases based on the average slope of several adja- child health and control of communicable disease. While cent data points; this was further refined visually this is of the utmost importance, it does not address the using a graph of the pressure waveform. Mean in- separate concern of providing care to those patients who spiratory pressure (IP), expiratory pressure (EP), and become critically ill in low-resource settings [7, 8]. respiratory rate (RR) during the first 5 min and the In this pilot study of an improvised CPAP system, last 5 min of each trial were calculated in Microsoft positive pressure ventilation was sustained in healthy Excel. Paired t tests were used for analysis of volunteers over a period of 30 min without any detect- significance. able CO2 retention or significant changes in subjects’ Trends in subjects’ HR, SpO2, and EtCO2 throughout vital signs. The system was well tolerated by all study the trial session were analyzed for significance with participants. A small decrease in airway pressure was ob- repeated-measures ANOVA (IBM SPSS). The post-trial served throughout the course of the trial, which may be questionnaire was analyzed using numerical averages of explained by mask leak or splashing of water out of the each Likert scale item. pressure reservoir. While the iCPAP system is similar in principle to neonatal bubble CPAP, it poses theoretical Results challenges as the adult face mask renders it a closed sys- The system maintained positive airway pressure for the tem with the potential risk of CO2 retention or danger- full trial period in all subjects, with mean EP of ous airway overpressure. This study provides an 5.1 cmH2O (SD 0.7) and mean IP of 3.2 cmH2O (SD encouraging proof-of-concept for this approach. While 0.8) over both measured time periods. A small but the current study examined a relatively low PEEP value significant decrease in mean expiratory pressure was of 5 cmH2O, the pressure administered can be increased observed over the course of the trial (5.3 vs 4.9 cmH2O, by fixing the exhalation limb at a greater depth. Limited p = 0.03), as well as a trend toward decreasing inspira- experimentation with higher pressure values suggests tory pressure (3.3 vs 3.1 cmH2O, p = 0.22; Fig. 4). No that 8.0 cmH2O of PEEP can be reliably maintained by significant effect of time on HR (F [29,261] = 0.915, the device; we did not attempt to increase the pressure p =0.595), SpO2 (F [29,261] = 0.976, p = 0.505), or above this level. EtCO2 (F [5,45] = 0.208, p = 0.958) was seen during As a pilot study, this trial does not address the poten- the trial (Fig. 5). There was no significant difference tial challenges of implementing the iCPAP system in a in mean RR between the two measured time periods field setting. One challenge is the flow of air required to (14.1 vs 15.5 breaths per minute, p =0.2). generate airway pressure, as many LMIC hospital set- The system was ranked an average of 4.0 on a 1–5 tings may not have a centralized air pressure system. A scale for overall comfort (with 5 = very comfortable). low-cost neonatal bubble CPAP system has been suc- cessfully implemented in Ghana using aquarium air Conclusions pumps to generate the required pressure [13, 14], and The majority of recent global health efforts have concen- higher-output ambient air pumps could be used in a trated on population-based care such as maternal and field-ready iCPAP device, such as oil-free air compressor

Fig. 4 Airway pressure over time. Graphs reflect expiratory pressure (EP) and inspiratory pressure (IP) during the sampled periods within the first 5 min (0–5) and last 5 min (25–30) of each trial. Each line represents a single participant Milliner et al. International Journal of Emergency Medicine (2019) 12:7 Page 5 of 6

Fig. 6 Model of low-tech pressure-limiting system. The cap on the unused Y connector has been replaced with a paper cover (arrow). Monitoring equipment has been omitted for the sake of clarity

Further studies should trial the iCPAP system in pa- tients with respiratory distress in resource-limited set- Fig. 5 Heart rate, oxygen saturation, and end-tidal CO2 versus time. tings where ventilator-based CPAP is not available. Each line represents a single participant Measurement of end-tidal CO2 or blood pCO2 should be conducted during initial field studies as the risk of CO2 retention in a patient with a rapid respiratory rate pumps utilized for powering tools and inflating vehicle remains unknown. tires. Another challenge is the availability of the face mask Additional file and pop-off valve used in constructing the system. A simple anesthesia face mask fitted with a head harness Additional file 1: Post-trial questionnaire. (DOCX 13 kb) can be used if alternative masks are not available; this setup is frequently used for pre-oxygenation prior to sur- Abbreviations gical procedures. Regarding the pop-off valve, limited CPAP: Continuous positive airway pressure; EP: Expiratory pressure; experimentation suggests that a simple alternative can etCO2: End-tidal carbon dioxide; HR: Heart rate; iCPAP: Improvised be constructed using a piece of tissue paper attached continuous positive airway pressure; IP: Inspiratory pressure; RR: Respiratory with a rubber band to the unused end of the system’sY rate; SpO2: Oxygen saturation connector (Fig. 6); this or similar alternatives may be Acknowledgements further explored depending on locally available The authors would like to acknowledge the staff of the Elmhurst Hospital materials. Simulation Center for their assistance with this trial. Milliner et al. International Journal of Emergency Medicine (2019) 12:7 Page 6 of 6

Funding 9. Martin S, Duke T, Davis P. Efficacy and safety of bubble CPAP in neonatal No external funding was obtained for the design, preparation, or reporting care in low and middle income countries: a systematic review. Arch Dis of this study. Child Fetal Neonatal Ed. 2014;99(6):F495–504. 10. Myhre J, Immaculate M, Okeyo B, et al. Effect of treatment of premature Availability of data and materials infants with respiratory distress using low-cost bubble CPAP in a rural The datasets used and analyzed during the current study are available from African hospital. J Trop Pediatr. 2016;62(5):385–9. the corresponding author on reasonable request. 11. Agarwal S, Maria A, Roy MK, Verma A. A randomized trial comparing efficacy of bubble and ventilator derived nasal CPAP in very low birth weight Authors’ contributions neonates with respiratory distress. J Clin Diagn Res. 2016;10(9):Sc09–sc12. BHM designed the study protocol, designed and assembled the airway 12. Rezzonico R, Caccamo LM, Manfredini V, et al. Impact of the systematic device, carried out experimental testing, performed the data analysis, and introduction of low-cost bubble nasal CPAP in a NICU of a developing country: was a major contributor to the manuscript. SB contributed to designing the a prospective pre- and post-intervention study. BMC Pediatr. 2015;15:26. study protocol, carried out experimental testing, and was a major contributor 13. Kawaza K, Machen HE, Brown J, et al. Efficacy of a low-cost bubble CPAP to the manuscript. JD contributed in the design of the airway device and system in treatment of respiratory distress in a neonatal ward in Malawi. experimental protocol and contributed in writing the manuscript. All authors PLoS One. 2014;9(1):e86327. read and approved the final manuscript. 14. Brown J, Machen H, Kawaza K, et al. A high-value, low-cost bubble continuous positive airway pressure system for low-resource settings: Ethics approval and consent to participate technical assessment and initial case reports. PLoS One. 2013;8(1):e53622. All subjects gave written consent prior to inclusion. The research protocol was approved by the Mount Sinai Hospital and Elmhurst Hospital IRBs in New York City, NY. The iCPAP device was classified as IDE-exempt by the FDA.

Consent for publication Not applicable.

Competing interests The authors declare that they have no competing interests.

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Author details 1Division of Emergency Medicine, University of Utah, 30 N 1900 E 1C026, Salt Lake City, UT 84132, USA. 2Simulation Center at Elmhurst and Department of Emergency Medicine, Elmhurst Hospital Center, Elmhurst, NY, USA. 3Departments of Emergency Medicine and , Icahn School of Medicine at Mount Sinai, 3 East 101st Street, Box 1620, New York, NY 10029, USA. 4Department of , Aurora St. Luke’s Medical Center, 2900 W Oklahoma Ave, Milwaukee, WI 53215, USA.

Received: 19 October 2018 Accepted: 15 February 2019

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